The introduction of statins (e.g. Mevacor@, Lipitor@) has reduced mortality from heart attack and stroke by about one-third. However, heart attack and stroke remain the major cause of death and disability, particularly in the United States and in Western European countries. Heart attack and stroke are the result of a chronic inflammatory condition, which is called atherosclerosis.
Several causative factors are implicated in the development of cardiovascular disease including hereditary predisposition to the disease, gender, lifestyle factors such as smoking and diet, age, hypertension, and hyperlipidemia, including hypercholesterolemia. Several of these factors, particularly hyperlipidemia and hypercholesteremia (high blood cholesterol concentrations) provide a significant risk factor associated with atherosclerosis.
Cholesterol is present in the blood as free and esterified cholesterol within lipoprotein particles, commonly known as chylomicrons, very low density lipoproteins (VLDLs), low density lipoproteins (LDLs), and high density lipoproteins (HDLs). Concentration of total cholesterol in the blood is influenced by (1) absorption of cholesterol from the digestive tract, (2) synthesis of cholesterol from dietary constituents such as carbohydrates, proteins, fats and ethanol, and (3) removal of cholesterol from blood by tissues, especially the liver, and subsequent conversion of the cholesterol to bile acids, steroid hormones, and biliary cholesterol.
Maintenance of blood cholesterol concentrations is influenced by both genetic and environmental factors. Genetic factors include concentration of rate-limiting enzymes in cholesterol biosynthesis, concentration of receptors for low density lipoproteins in the liver, concentration of rate-limiting enzymes for conversion of cholesterols bile acids, rates of synthesis and secretion of lipoproteins and gender of person. Environmental factors influencing the hemostasis of blood cholesterol concentration in humans include dietary composition, incidence of smoking, physical activity, and use of a variety of pharmaceutical agents. Dietary variables include amount and type of fat (saturated and polyunsaturated fatty acids), amount of cholesterol, amount and type of fiber, and perhaps amounts of vitamins such as vitamin C and D and minerals such as calcium.
Low density lipoprotein (LDL) oxidation has been strongly implicated in the pathogenesis of atherosclerosis. High density lipoprotein (HDL) has been found to be capable of protecting against LDL oxidation, but in some instances has been found to accelerate LDL oxidation. Important initiating factors in atherosclerosis include the production of LDL-derived oxidized phospholipids.
Normal HDL has the capacity to prevent the formation of these oxidized phospholipids and also to inactivate these oxidized phospholipids once they have formed. However, under some circumstances HDL can be converted from an anti-inflammatory molecule to a pro-inflammatory molecule that actually promotes the formation of these oxidized phospholipids.
HDL and LDL have been suggested to be part of the innate immune system (Navab et al. (2001) Arterioscler Thromb Vasc Biol. 21: 481-488). The generation of anti-inflammatory HDL has been achieved with class A amphipathic helical peptides that mimic the major protein of HDL, apolipoprotein A-I (apo A-I) (see, e.g., WO 02/15923).